CHE1501 May/Jun 2016 exam paper — questions

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Every question, by topic

  1. Question 1.1 · Atomic structure and the periodic table · 3 marks

    For the naturally occurring isotope represented as chlorine-36 with atomic number 17 and written as ^36_17Cl^-, state the number of protons, the number of neutrons, and the number of electrons present.Show the full question

  2. Question 1.2 · Atomic structure and the periodic table · 3 marks

    Give an explanation of what the term isotopes means, and then state whether fluorine-19 (written as ^19_9F) and fluorine-20 (written as ^20_9F) would be considered isotopes of each other.Show the full question

  3. Question 1.3 · Atomic structure and the periodic table · 2 marks

    Write down the chemical formula of copper(II) hydroxide.Show the full question

  4. Question 1.4 · Atomic structure and the periodic table · 2 marks

    An atom has the electron configuration ns2np5 in its outermost occupied shell. Identify the group of the periodic table to which this atom belongs, and state what the elements of this group are commonly called.Show the full question

  5. Question 1.5 · Atomic structure and the periodic table · 4 marks

    Give the set of four quantum numbers that describe the valence electron of a rubidium (Rb) atom.Show the full question

  6. Question 1.6 · Atomic structure and the periodic table · 3 marks

    Draw the general shapes of the s orbital and the p orbital.Show the full question

  7. Question 1.7 · Atomic structure and the periodic table · 8 marks

    Draw the Lewis structures of the BrF4^- ion and the BF4^- ion, using lines to represent bonds and showing all lone pairs. State how many valence electrons are present in each of these two molecules/ions. Then, using VSEPR theory, explain why BrF4^- adopts a square planar shape while BF4^- adopts a tetrahedral shape.Show the full question

  8. Question 2.1 · Chemical bonding and Lewis structures · 4 marks

    For each of the three molecules NaI, H—Br and Cl—Cl, classify the bond as ionic, polar covalent or non-polar covalent, and for the polar bond indicate the direction of polarity using the correct symbol.Show the full question

  9. Question 2.2 · Chemical bonding and Lewis structures · 2 marks

    Determine the number of lone electron pairs present in the phosphine molecule, PH3, and state the molecular geometry of this molecule.Show the full question

  10. Question 2.3 · Chemical bonding and Lewis structures · 3 marks

    Work out the oxidation number of the following atoms: (i) calcium (Ca) in CaCl2; (ii) nickel (Ni) in Ni(OH)2; (iii) oxygen (O) in H2O2.Show the full question

  11. Question 2.4 · Chemical bonding and Lewis structures · 2 marks

    State whether you would use an acid, a base, an oxidizing agent, a reducing agent or a precipitating agent to convert NO2^- to N2.Show the full question

  12. Question 2.5 · Chemical bonding and Lewis structures · 2 marks

    State whether you would use an acid, a base, an oxidizing agent, a reducing agent or a precipitating agent to convert NO2^- to HNO2.Show the full question

  13. Question 2.6 · Chemical bonding and Lewis structures · 5 marks

    At 900°C, titanium tetrachloride (TiCl4) vapour reacts with molten magnesium metal (Mg) to produce solid titanium metal and molten magnesium chloride. Write a balanced chemical equation for this reaction, and identify which substance is being oxidized and which is being reduced.Show the full question

  14. Question 2.7 · Chemical bonding and Lewis structures · 1 mark

    Classify the reaction 2Ag2O (s) → 4Ag (s) + O2 (g) as one of the following reaction types: combination, combustion, decomposition, precipitation, acid-base, neutralization or redox.Show the full question

  15. Question 3.1 · Stoichiometry and solutions · 8 marks

    Styrene is a substance used in the manufacture of polystyrene cups and insulation. It is composed of 92.3% carbon and 7.7% hydrogen by mass, and its molar mass is 104 g/mol. Determine the empirical formula and the molecular formula of styrene.Show the full question

  16. Question 3.2 · Stoichiometry and solutions · 2 marks

    Write down the equation used to calculate percentage yield.Show the full question

  17. Question 3.3 · Stoichiometry and solutions · 4 marks

    Calculate the molarity of a KF(aq) solution that contains 116.2 g of KF dissolved in 3.00 L of solution.Show the full question

  18. Question 3.4 · Stoichiometry and solutions · 4 marks

    You wish to synthesise magnesium oxide and are provided with 1.00 mol of Mg and 0.252 mol of iron(III) oxide. The balanced equation for the reaction is 3Mg + Fe2O3 → 3MgO + 2Fe. Determine the limiting reagent in this reaction and calculate the theoretical yield, in grams, of MgO that can be produced.Show the full question

  19. Question 3.5 · Stoichiometry and solutions · 4 marks

    Suppose you were using the Haber reaction to synthesise ammonia, represented by N2(g) + 3H2(g) ⇌ 2NH3(g), with ΔH = -91.8 kJ. Applying Le Chatelier's principle, name four changes you could make to your experimental setup to increase the overall yield of ammonia.Show the full question

  20. Question 4.1 · Redox reactions · 7 marks

    Using chemical equations, explain how the rusting of iron takes place, and explain why rusting occurs faster in a salt solution or in acid than it does in pure water.Show the full question

  21. Question 4.2 · Chemical equilibrium · 3 marks

    For the equilibrium 2A(g) + B(g) ⇌ C(g) + 3D(g), the equilibrium molar concentrations of the species are A = 1.0 M, B = 4.0 M, C = 4.0 M and D = 2.0 M. Calculate the value of the equilibrium constant, K.Show the full question

  22. Question 4.3 · Chemical equilibrium · 4 marks

    Explain how adding ammonia to water produces a basic solution, and write the chemical reaction showing the ions that are formed.Show the full question

  23. Question 4.4 · Chemical equilibrium · 2 marks

    Consider the reaction Li2O(g) + H2O(l) → 2Li+(aq) + 2OH-(aq). State which of the acid/base theories (i.e. Bronsted-Lowry, Arrhenius or Lewis) best describes Li2O(g), and briefly motivate your answer.Show the full question

  24. Question 4.5 · Chemical equilibrium · 8 marks

    Formic acid (HCO2H) is secreted by ants. Calculate the pH of a 0.0025 M solution of formic acid, given that Ka = 3.5 x 10^-8.Show the full question

  25. Question 5.1 · Gas laws and kinetic theory · 2 marks

    Three sealed tanks, labelled X, Y and Z, all have the same volume and the same temperature. In each tank one mole of CH4 is represented by a circle, one mole of oxygen (O2) by a square, and one mole of SO2 by a triangle. No reaction takes place between these molecules. Tank X contains 5 circles, 2 triangles and 1 square. Tank Y contains 2 circles, 4 triangles and 3 squares. Tank Z contains 3 circles, 1 triangle and 3 squares. Based on the diagrams of tanks X, Y and Z (each containing circles representing CH4, squares representing O2, and triangles representing SO2, all at the same volume and temperature), state in which of the three tanks the total pressure is highest.Show the full question

  26. Question 5.2 · Gas laws and kinetic theory · 2 marks

    Three sealed tanks, labelled X, Y and Z, all have the same volume and the same temperature. In each tank one mole of CH4 is represented by a circle, one mole of oxygen (O2) by a square, and one mole of SO2 by a triangle. No reaction takes place between these molecules. Tank X contains 5 circles, 2 triangles and 1 square. Tank Y contains 2 circles, 4 triangles and 3 squares. Tank Z contains 3 circles, 1 triangle and 3 squares. Referring to the same three sealed tanks X, Y and Z, state in which tank the partial pressure of SO2 is highest.Show the full question

  27. Question 5.3 · Gas laws and kinetic theory · 3 marks

    Three sealed tanks, labelled X, Y and Z, all have the same volume and the same temperature. In each tank one mole of CH4 is represented by a circle, one mole of oxygen (O2) by a square, and one mole of SO2 by a triangle. No reaction takes place between these molecules. Tank X contains 5 circles, 2 triangles and 1 square. Tank Y contains 2 circles, 4 triangles and 3 squares. Tank Z contains 3 circles, 1 triangle and 3 squares. Referring to the same three sealed tanks X, Y and Z, determine in which tank the total mass of all three gases (CH4, O2 and SO2) is the same.Show the full question

  28. Question 5.4 · Gas laws and kinetic theory · 3 marks

    Three sealed tanks, labelled X, Y and Z, all have the same volume and the same temperature. In each tank one mole of CH4 is represented by a circle, one mole of oxygen (O2) by a square, and one mole of SO2 by a triangle. No reaction takes place between these molecules. Tank X contains 5 circles, 2 triangles and 1 square. Tank Y contains 2 circles, 4 triangles and 3 squares. Tank Z contains 3 circles, 1 triangle and 3 squares. Referring to the same three sealed tanks X, Y and Z, determine which tank has the heaviest contents overall.Show the full question